Add new IDBFactory.prototype.databases() API to externs
Add new IDBFactory.prototype.databases() API to externs

TypeScript 4.4 added the new IDBFactory.prototype.databases() API (https://www.w3.org/TR/IndexedDB/#dom-idbfactory-databases) to the standard lib.dom.d.ts typings. This adds it to the default JavaScript externs.

PiperOrigin-RevId: 396812006

google/elemental2,google/elemental2